01 V70 Vacuum leak

"Arnold" escreveu na mensagem news:NplIi.5727$603.714@trndny02...

Again from engine vacuum.

Usually the cause is some previous repair where the mechanics brakes the hose when repairing anything else. The less goings to the work shop the best.

Basically you need to locate where is the hissing sound comming from. From the engine compartiment, or from the interior of the car.

That's no vacuum pump, so that vacuum always comes from the engine intake manifold.

Thanks for your reply, What I was asking was if the vacuum source for the AC actuators and the brake booster are coming from 2 different places on the intake manifold, so I could isolate the vacuum leak by plugging one hose at the time in the engine compartment. I could not do that if they were fed by the same point, and split with a Tee downstream, or if the actuators are fed from the brake booster. The hissing sound appears to be coming from an area under the steering wheel. I will not have access to the vehicle for another 7 to 10 days. Thanks

Arnold

Best chance that it is the brake booster very common complaint nothing to rebuild just replace the brake booster. The noise will get worse @ some point & the power brake's will slowly start to get harder to press Glenn

"Arnold" escreveu na mensagem news:NSCIi.15345$No2.4644@trndny07...

Look, vacuum is changing all the time. You can have hard vacuum under heavy decceleration, and no vacuum at all when the turbo is at full pressure. So, the hissing sound must change accordingly.

Hissing sounds may have many sources. You need to find the patern, when it changes sound, and so on.

Brakes is hard to believe - large independent hose with an anti-return valve. The AC actuators could be, but again vacuum changes all the time inside the intake manifold. There is a small vacuum hose for the turbo indicator too.

Are you sure it is a vacuum related problem?

If its a gasoline car, usually vacuum problems causes the "engine failure" lamp to light (lambda sensor), due to a faulty air intake.

Hi Mr. Albuquerque, you are correct, the hissing noise changes per driving condition, under acceleration, or when climbing a hill, it is barely perceptible, however, when the car idles, it is very noticeable. Have not had the "Check engine light on" yet, maybe the computer tries to compensate the mixture based on the O2 sensor, but I sure would like to eliminate the leak and avoid running it like this. Thanks a lot for your help. Something else I should check is if after I shut the car off, there is enough vacuum in the brake booster reservoir to apply the brake once, if I can, then I know for sure the leak is elsewhere because the check valve would hold the vacuum in the brake booster.

"Arnold" escreveu na mensagem news:wrGIi.15360$No2.12090@trndny07...

If so, your vacuum hypotesis is quite good. At idle you get a steady situation with a good vacuum to test all the hypotesis of a leak.

So, its a small leak. There are many small hoses hidden below the intake manifold, some go down to the turbo. The engine is very complicated to work with (very compact).

Check the turbo indicator hose that shoud go up to the instruments pannel (I belive), since its a direct indicator of the vacuum and could be itself the responsible. And the AC actuators vacuum too.

Brakes system is all inside the engine compartement and most certainly a small leak cannot be heard inside the car, since those cars are very well sound isolated.